Electronic musical instrument capable of modulation controlling a second keyboard section tone signal in accordance with a first keyboard section tone signal

ABSTRACT

An electronic musical instrument is capable of modulation controlling at least one of the pitch frequency, tone color and volume envelope of a second keyboard section tone signal by a tone signal obtained by operating any key on the first keyboard section. To control the frequency, tone color and volume envelope of the second keyboard section tone signal, a voltage controlled oscillator, voltage controlled filter and voltage controlled amplifier can be used. The first keyboard section tone signal may be frequency divided and/or waveform converted so as to control the second keyboard section tone signal.

United States atent 1191 Okamoto June 3, 1975 [54] ELECTRONIC MUSICAL INSTRUMENT 238C221 I N ac 1 KEYBOARD 3,610,804 10/1971 Matsuura 84/1.l7 3,619,469 11/1971 Adachi t. 84/1.17 SECTION TONE SIGNAL IN ACCORDANCE 3,671,659 6/1972 Suzuki 84/1.17 WITH A FIRST KEYBOARD SECTION TONE 3,672,253 6/1972 Hiyama... 84/l.l7 X SIGNAL 3,697,664 10/1972 Hiyama.... 84/1.17 3,707,594 12/1972 lchikawa.. 84/l.17 X lnvemorl Eisaku Okamoto, Hamakfla, Japan 3,717,715 2/1973 Jordy 84/1.17 3,723,633 3/1973 Adachi..... 84/1.01 [73] Assgnee' g i 3,749,807 7/1973 Adachi 84/1. 17 4 am p 3,767,833 10/1973 Noble Ela1..... 84/1.01 2 M 8 1974 3,803,338 4/1974 Adachi 84/1.17 [22] F1 ed ay 3,819,843 6/1974 Okamotom, 84/1.1 [21] Appl. No.2 467,892 3,828,110 8/1974 Colin 84/1.0l

. Primary Examiner-Stephen .1. Toms'ky D [3O] Forelgn Apphcauon Pnomy ata Assistant ExaminerStanley J. Witkowskr lsvlay 181,l1997733 .JIapan ..4 281-35227] Attorney, Agent, or Firm Flynn & Frishauf ept. apan Sept. 8, 1973 Japanm. 48-105448 [57] ABSTRACT [52] U 5 Cl 84/1 84/122. An electronic musical instrument is capable of modu- I 7 84/124 lation controlling at least one of the pitch frequency, [51] Int Cl 7 Glob 1/04. Gloh 5/00 tone color and volume envelope of a second keyboard [58] Field 01 1 17 1 DIG 2 section tone signal by a tone signal obtained by oper- 84/DIG 8 5 6 1 ating any key on the first keyboard section. To control 1 5 126 i the frequency, tone color and volume envelope of the second keyboard section tone signal, a voltage cond trolled oscillator, voltage controlled filter and voltage [56] g gg zf lIJZTENTS controlled amplifier can be used. The first keyboard UNIT section tone signal may be frequency divided and/or george waveform converted so as to control the second key- 1 3, eorge 3,557,295 1/1971 Adachi 84/l.19 x board Section tone slgnal 3,567,838 3/1971 Tennes et a1. 84/101 13 Claims, 5 Drawing Figures 14a o g V C O V C F V C A E l 190 200 m CONTFOL E :ig VOLTAGE GEN c v 6 5E E 16 17 u) E9, 8 m

56331151511116 E QEE HQ VOLTAGE GEN.

EXPRESSION CONTROL 23, 2b 24 25 13b 15b v c o v c F v c A 0 1 z m E 10B l 9b 2 Ob Eg-1cvs| -1CVG CV01 0% 1(/) 1 r, 1- OJ :0 O.

28894811118 Egg/58mg VOLTAGE GEN. r

CTION Jib PITCH DETERMINING PAI'IZI-IIEUJUHS 1975 3,886, 834 SHEET 1 PITCH DETERMINING F I I 2 s g V C O V C F v c A l R96 290 CONTROL I w $EI VOLTAGE GEN l C V G C v G 3 92 A 0:9 186 I: 16 I7 (I) o Tl Uzi] I I g N rI lEfiue KEY ARlj VOLTAGE GENJVZIO I60 TION EXPRESSION CONTROL 23 2 k} 25 v c o v c F v c A 'VW- 0: :5 a P *g g 3% c v c; c v 6 v G I-(T) A F *3 k I (DI%RNAI'FAI(EDEE\IG kIZ- Y SSARD VOLTAGE GEN? 24b SECTION Hb I AI'EIIIEIIJUIQ I975 SHEET FIG.2

KEYBOARD SECTION PITCH DETERMINING VOLTAGE TO VCO AND VCF L m R TE LNG AOA @W UN RI E TSm V G o LHI 1 O -I kHlIfi 1 1'0 3 I MMHIIIQ K w m K 0 1s a IIAIL IAIIIL O S 2 ND DECAY TIME P KEY RELEASED 4ST DECAY TIME ATTACK TIME ATTACK LEVEL NORMAL LEVEL INITIAL LEVEL CUTOF F LEVEL KEY DEPRESSED BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION It is the object of this invention to provide an electronic musical instrument capable of modulation controlling a second tone signal obtained in response to a key operation on a second keyboard section by a first tone signal obtained in response to key operation on a first keyboard section, whereby a diversified performance effect can be attained.

According to this invention a second tone'signal has any one or at least one of its pitch frequency, tone color and volume envelope modulated by a first tone signal.

The first and second tone signals may be ones detrolled by those control voltages from control voltage rived, in response to key operation, from conventional tone generators including master oscillators and frequency dividers.

According to a preferred embodiment of this invention, the above-mentioned second tone signal is formed by a voltage controlled oscillator in response to that pitch determining voltage of a magnitude corresponding to the note of any operated key which is derived from a pitch determining voltage source in response to the key operation. To the second tone signal a tone color and volume envelope are imparted by a voltage controlled filter and voltage controlled amplifier, respectively. The above-mentioned first tone' signal is coupled as a control voltage to any one or at least one of a voltage controlled oscillator, voltage controlled filter and voltage controlled amplifier so as to control at least one of the pitch frequency, tone color and volume envelope of the second tone signal. In this case, the first tone signal may be selectively coupled through switches 'to one of voltage controlled oscillator, voltage controlled filter and voltage controlled amplifier.

The first tone signal, like the second tone signal, may be formed by a voltage controlled oscillator in response to a pitch determining voltage which is obtained from a pitch determining voltage source in response to key operation. The output of the voltage controlled oscillator, like the second tone signal, may be coupled to the voltage controlled filter and voltage controlled amplifier.

The voltage'controlled oscillator, voltage controlled filter and voltage controlled amplifier associated with the first tone signal and the voltage controlled oscillator, voltage controlled filter and voltage controlled amplifier associated with the second, tone signal are congenerators which are varied with time during the key depression time and during the key release time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an electronic musical instrument according to one embodiment of this inven tlon;

FIG. 2 isa circuit arrangement ofa keyboard section of FIG. 1;

FIG. 3 shows the waveforms of control voltages formed by control voltage generators of FIG. 1; and

FIGS. 4 and 5 are block diagrams showing the other embodiments of this invention.

DESCRIPTION OF THE PREFERRED- EMBODIMENTS In FIG. 1 showing one emodiment of this invention, the reference numerals 11a and 11b denote upper and lower keyboard sections where a pitch determining voltage having a magnitude corresponding to the note of any operated key and a trigger signal indicating a key operation are generated. To the upper and lower keyboard sections lla and 11b musical tone signal producing circuits 12a and 12b are respectively coupled. The musical tone signal producing circuit 12a includes a voltage controlled oscillator (hereinafter referred to as VCO) 13a for generating'in response to a pitch determining voltage from the upper keyboard section 11a a tone signal having a frequency corresponding to the note of operated key; voltage controlled filter (hereinafter referred to as VCF) 14a for imparting a tone color to the tone signal from VCO; and voltage controlled amplifier (hereinafter referred to as VCA) 15a for imparting a volume envelope to an output signal of VCF. To VCF 14a is also coupled the pitch determining voltage from the keyboard section 110. Likewise, the musical tone signal producing circuit 12b includes a VCO 13b, VCF 14b and VCA 15b.

. The outputs of the musical tone signal producing circuits. 12a and 12b are coupled to sound reproducing means including an amplifier l6 expression control 162 and loudspeaker 17.

The musical tone signal producing circuit 12a further includes control voltage generators 18a, 19a and 20a provided correspondingly to VCO 13a, VCF 14a and VCA 15a so as to control the tone pitch, tone color and volume envelope of the tone signal. The control voltage generators 18a, 19a and 20a are adapted to generate in response to a trigger signal from the keyboard section Ila voltage signals having various parameters set at a parameter controlling voltage generator 21a to thereby control VCO 13a, VCF 14a and VCA 15a. Likewise, the musical tone signal producing circuit 12b includes control voltage generators 18b, 19b and 20b for generating control voltages in response to a trigger signal from the keyboard section llb so as to control VCO 13b, VCF 14b and VCA 15b, and a parameter controlling voltage generator, 22b for supplying parameter controlling voltages to these control voltage generators the unlabeled resistors in FIG. 1 which are connected to VCO 13b, VCF 14b and VCA' 15b are conventional mixing resistors.

Fig. 3 shows, by way of example, control voltage waveforms obtained from the control voltage generators 18a to 20a and 18b to 20b. In the control voltage waveforms shown, A shows the control voltage waveform as applied to VCOs 13a and 13b and VCFs 14a and 14b, while B shows the control voltage waveform as applied to VCAs 15a and 15b. Waveforms A and B are' similar, but their nominal voltage levels are different. When the key is depressed, the voltage waveform A rises from an initial level to an attack level during an attack time and decays from the attack level to a normal level during a first decay time. The normal level continues until the key is released. Upon release of the key, the voltage waveform decays from the normal level to the initial level during a second decay time.

When the voltage waveform A is supplied to VCOs 13a and 13b, the tone signal is so controlled during the key depression time that its frequency is abruptly varied from an initial level frequency somewhat lower than a normal level frequency to an attack level frequency somewhat higher than the normal level frequency which is determined by the pitch determining voltage from the keyboard section. Thereafter, the tone signal frequency approaches to the normal level frequency during the first decay time and becomes equal to the normal level frequency after lapse of the first decay time. After the key is released, the tone signal frequency is lowered from the normal level frequency to the initial level frequency during the second decay time. Namely, the tone signal frequencies from VCOs 13a and 13b are modified in accordance with the waveform of voltages varied with time.

When the voltage waveform A is supplied to VCFs 14a and 14b, the cutoff frequencies of the filter are controlled in accordance with the voltage waveform.

Consequently, the tone color of the tone signal is modified.

When the key is depressed, the voltage waveform B rises from a cutoff level to a peak level and, after lapse of an attack time, is returned to a sustain level during a first decay time. The sustain level is maintained until the key is released. After release of the key, the waveform decays from the sustain level to the cutoff level during a second decay time. Upon supply of the voltage waveform B to VCAs 15a and 15b an envelope as shown in the waveform B is imparted to the tone signal. It will be understood that, if the waveform B is not applied to VCAs 15a and 15b, the VCAs each act as a tone keyer, since they are in the cutoff state.

The parameter controlling voltage generators 21a and 21b, described in copending applications Ser. Nos. 457,656 and 462,398, both assigned to the same Assignee, as the present application, each have a power source and a plurality of potentiometers and are adapted to apply to the respective control voltage generators voltage for controlling -various controlled parameters of control voltages from the respective'control voltage generators. The control voltages applied to VCO and VCF have such controlled parameters as, for example, a normal level, attack level, initial level, attack time, first decay time and second decay time, while, on the other hand, the control voltage applied to VCA has such controlled parameters as a sustain level, attack time, first decay time and second decay time. In FIG. 1 and throughout the drawings, the thick arrows coupling blocks together represent a plurality of signal lines.

FIG. 2 shows the arrangement of the keyboard section for supplying a pitck determining voltage to VCO. The voltage of a power source E is divided by a voltage dividing circuit network including resistors R1 and R2.

To the respective voltage dividing points are connected the normally open fixed contacts of key switches S1, S2 S3 actuated by keys K1, K2, K3 The movable contacts of the respective key switches are connected to the normally open fixed contacts of adjacentkey switches. In the key switch arrangement shown, when a plurality of keys are depressed at a time a voltage on a voltage dividing point connected to the key switch actuated by a single key is delivered to VCO. The key switches S1, S2, S3 are ganged with key switches S01, S02, S03 and at the time of key operation a trigger signal based on a power source E1 is supplied to the control voltage generators via a load resistor RL. The control voltage generators initiate the formation of control voltages upon receipt of the trigger signal.

With the electronic musical instrument so constructed, the tone pitch, tone color and volume envelope of tone signals obtained by actuating any keys on the upper and lower keyboard sections are modulated by control voltages whose values are varied with time during the key depression and during the key release. As a result, diversified musical sounds very pleasing to the human ears are obtained.

According to this invention a tone signal obtained from VCO 13a is coupled, through switches 23, 24 and 25, as an additional control voltage to VCO 13b, VCF 14b and VCA 15b in the second musical tone signal producing circuit 12b. The additional control voltage is added to a respective control voltage from control voltage generators l8b, 19b and 20b.

Upon closure of the switch 23, a tone signal from VCO 13a is applied, together with a control voltage formed at the control voltage generator 18b, to VCO 13b. For this reason, the tone signal of VCO 13b is roughly frequency modulated in accordance with the waveform of control voltage from the control voltage generator 18b and finely frequency modulated by the additional control voltage.

When the switch 24 is closed, VCF 14b has its cutoff frequency roughly varied by a control voltage from the control voltage generator 19b and finely varied by the additional control voltage.

Upon closure of the switch 25, VCA 15b has its gain mainly varied by a control voltage from the control voltage generator 20b and additionally varied by the additional control voltage from VCO 13a. Consequently, a rough envelope formed in accordance with the control voltage waveform of the control voltage generator 20b is imparted to the output tone signal of VCA 15b, and the output tone signal of VCA 15b has its envelope finely varied by the additional control voltage.

Though with the embodiment of FIG. 1 the output of VCO 13a is utilized as an additional control voltage, the'output of VCF 14a or VCA may be used as the additional control voltage. Though the additional control voltage is coupled through switches 23, 24 and 25 to VCO 13b, VCF 14b and VCA 15b, it may be coupled to any one of VCO 13b, VCF 14b and VCA 15b.

FIGS. 4 and 5 show the other embodiments of this invention. In these Figures, same reference numerals are employed to designate parts or elements corresponding to those shown in FIG. 1 and any further explanation is, therefore, omitted. Unlabelled resistors in FIGS. 4 and 5 are conventional mixing resistors.

With the embodiment of FIG. 1 a second tone signal associated with the lower keyboard section 11b is modulated by a first tone signal associated with the upper keyboard section 11a having a higher compass than the lower keyboard section 11b. Where, however, the frequency of the modulation signal is higher than the frequency of a signal to be modulated, unclearness is liaclearness it is desirable to couple the first tone signal associated with the upper keyboard section 11a to the second musical tone signal producing circuit 12b, as shown in FIG. 4, through a frequency divider 27.

With the embodiment of FIG. 5 a first tone signal associated with an upper keyboard section 11a is coupled through a waveform converter 30 to a second musical tone signal producing circuit 12b. In this case, a sawtooth wave 31 for example, of the second tone signal formed at VCO 13a may be converted by the waveform 30 into a plurality of different waveforms, for example, a rectangular waveform 32, triangular waveform 33, or sinusoidal waveform 34. These waveforms are selectively coupled through switches 35, 36 and 37 to the second musical tone signal producing circuit 12b. The use of the waveform converter 30 can provide more deversified performance effect. The waveform converter 30 may be used in combination with the frequency divider 27 shown in FIG. 4.

Though with the above-mentioned embodiments multi-stage keyboard type electronic musical instrument having the upper and lower keyboards has been explained, this invention can also be applied to a single keyboard type electronic musical instrument. In this case, the single keyboard is divided into right and left half sections and a second tone signal obtained by actuating any key on the left half keyboard section is controlled by a first tone signal obtained by actuating any key on the right half keyboard section. This invention can also be applied to a modulation control between a manual keyboard section and a pedal keyboard section.

What is claimed is:

1. An electronic musical instrument comprising:

a first keyboard section including a plurality of keys ble to occur due to modulation. To obviate such unand means for generating a pitch determining volt- 1 age having a magnitude which is a function of the note of an operated key;

a second keyboard section including a plurality of keys and means for generating a pitch determining voltage having a magnitude which is a function of the note of an operated key;

a first musical tone signal producing means connected to said first keyboard section and including a first voltage controlled oscillator means for generating in response to the pitch determining voltage a tone signal having a frequency which is a function of the note of the operated key on said first section;

a second musical tone signal producing means connected to said second keyboard section and including a second voltage controlled oscillator means for generating in response to the pitch determining voltage a tone signal having a frequency which is a function of the note of the operated key on said second keyboard section;

sound reproducing means connected to said first and second musical tone signal producing means; and

means for coupling a tone signal from said first musical tone signal producing means to said second voltage controlled oscillator means to thereby modulate the frequency of a tone signal produced by said second oscillator means.

2. An electronic musical instrument according to claim 1 wherein said last-mentioned means comprises means for dividing the frequency of the tone signal from said first musical tone signal producing means.

3. An electronic musical instrument according to claim 1 wherein. said last-mentioned means comprises waveform converting means for converting the waveform of the tone signal from said first musical tone signal producing means.

4. An electronic musical instrument according to claim 3 wherein said waveform converting means includes means to convert the waveform of the tone signal from said first musical tone signal producing means into a plurality of kinds of waveforms and includes switching means for selecting one of the waveforms.

5. An electronic musical instrument according to claim 1 wherein said coupling means includes means for coupling the output of said first voltage controlled oscillator means to said voltage controlled oscillator means.

6. An electronic musical instrument according to claim 1 wherein said second musical tone signal producing means further comprises a voltage controlled filter means connected to said voltage controlled oscillator means for imparting a tone color to the tone signal from said oscillator means, said voltage controlled filter means being operative to vary in response to a control voltage the frequency characteristic thereof; and further comprising means for coupling the tone signal from said first musical tone signal producing means to said voltage controlled filter means as the control voltage.

7. An electronic musical instrument according to claim 1 wherein said second musical tone signal producing means further comprises a voltage controlled amplifier means coupled to said second oscillator means, said amplifier means being operative to vary in response to a control voltage the gain thereof; and further comprising means for coupling the tone signal from said first musical tone signal producing means to said voltage controlled amplifier means as the control voltage.

8. An electronic musical instrument according to claim 1 wherein said first and second keyboard sections comprise means for generating in response to key operation first and second trigger signals indicating the key operation respectively; said first musical tone signal producing means comprises a first voltage controlled filter means coupled to said first oscillator means, a first voltage controlled amplifier means coupled to said voltage controlled filter means and first control voltage generating means responsive to the first trigger signal to generate control voltages which vary as a function of time and which are coupled to said first voltage controlled oscillator means, first voltage controlled filter means and first voltage controlled amplifier means; and wherein said second musical tone signal producing means comprises a second voltage controlled filter means coupled to said second oscillator means, a second voltage controlled amplifier means coupled to said second filter means, and second control voltage generating means responsive to the second trigger signal to generate control voltages which vary as a function of time and which are coupled to said voltage controlled oscillator means, second voltage controlled filter means and second voltage controlled amplifier means.

9. An electronic musical instrument comprising:

first and second keyboard sections each having a plurality of keys;

first and second musical tone signal producing means respectively coupled to said first and second keyboard sections for producing respective musical tone signals having pitch frequencies which are functions of the notes of keys operated on said respective first and second keyboard sections, at least said second musical tone signal producing means comprising a voltage controlled means for controlling at least one of the pitch frequency, tone color, and volume envelope of a musical tone signal generated by said electronic musical instrument;

sound reproducing means coupled to said first and second musical tone signal producing means for generating a musical sound; and

means for coupling said voltage controlled means a tone signal obtained from said first musical tone signal producing means in response to key operation on said first keyboard section for controlling said voltage controlled means.

10. An electronic musical instrument comprising:

a first keyboard section for generating a first pitch determining voltage having a magnitude which is a function of the note of an operated key and a first trigger signal indicating the key operation on said first keyboard section;

a second keyboard section for generating a second pitch determining voltage having a magnitude which is a function of the note of an operated key and a second trigger signal indicating the key operation on said second keyboard section;

a first musical tone signal producing means coupled to said first keyboard section and including a first voltage controlled oscillator means for generating in response to the pitch determining voltage from said first keyboard section a tone signal having a pitch frequency which is a function of the note of the operated key, a first voltage controlled filter means coupled to said first voltage controlled oscillator means, a first voltage controlled amplifier means coupled to said first voltage controlled filter means, and first control voltage generating means responsive to the first trigger signal to generate control voltages which vary as a function of time and which are coupled to said first voltage controlled oscillator means, voltage controlled filter means and voltage controlled amplifier means, said first voltage controlled oscillator means, voltage controlled filter means and voltage controlled amplifier means being operative to vary in response to the control voltages, the oscillator frequency of said first voltage controlled oscillator means, the frequency characteristic of said first voltage controlled filter means and the gain of said first voltage controlled amplifier means; a second musical tone signal producing means coupled to said second keyboard section and including a second voltage controlled oscillator means for generating in response to the pitch determining voltage from said second keyboard section a tone signal having a pitch frequency which is a function of the note of the operated key, a second voltage controlled filter means coupled to said second voltage controlled oscillator means, a second voltage controlled amplifier means coupled to said second voltage controlled filter means, and a second control voltage generating means responsive to the second trigger signal to generate control voltages which vary as a function of time and which are coupled to said second voltage controlled oscillator means, voltage controlled filter means and voltage controlled amplifier means, said second voltage controlled oscillator means voltage controlled filter means and voltage controlled amplifier means being operative to vary in response to the control voltages the oscillation frequency of said second voltage controlled oscillator means, the frequency characteristic of said second voltage controlled filter means and the gain of said second voltage controlled amplifier means; second reproducing means coupled to said first and second musical tone signal producing means; and

means for coupling as an additional control voltage an output signal from said first voltage controlled oscillator means in said first musical tone signal producing means to at least one of said second voltage controlled oscillator means, second voltage controlled filter means and second voltage controlled amplifier means in said second musical tone signal producing means.

11. An electronic musical instrument according to claim 10 wherein said last-mentioned means comprises switching means for selectively coupling the output signal from said first voltage controlled oscillator means to one of said second voltage controlled oscillator means, second voltage controlled filter means and second voltage controlled amplifier means.

12. An electronic musical instrument according to claim 10 wherein said last-mentioned means comprises means for dividing the frequency of the output signal from said first voltage controlled osicllator means, means.

13. An electronic musical imstrument according to claim 10 wherein said last-mentioned means comprises means for changing the waveform of the output signal from said first voltage controlled oscillator means, first. l l l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3 4 DATED June 3 1975 INVEN t 1 Eisaku OKAMOTO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 19, before "voltage controlled" insert second-;

Column 8, line 48, change "osicllator" to -oscillator; after "means" delete and insert line 49, delete "means."

line 53, after "means delete first" Signed and Scaled this second Day of Decemberlflj [SEAL] Attest:

RUTH C. MASON C. MARSHALL DAN" Arresting Officer Commissioner of Patents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,886,834 DATED June 3 1975 INV N 1 Eisaku OKAMOTO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, I

Column 8,

[SEAL] line 19, before "voltage controlled" insert -second-;

line 48, change "osicllator" to -oscillator; after "means" delete and insert line 49, delete "means."

RUTH C. MASON Arresting Officer C MARSHALL DANN Commissioner oflatenls and Trademarks 

1. An electronic musical instrument comprising: a first keyboard section including a plurality of keys and means for generating a pitch determining voltage having a magnitude which is a function of the note of an operated key; a second keyboard section including a plurality of keys and means for generating a pitch determining voltage having a magnitude which is a function of the note of an operated key; a first musical tone signal producing means connected to said first keyboard section and including a first voltage controlled oscillator means for generating in response to the pitch determining voltage a tone signal having a frequency which is a function of the note of the operated key on said first section; a second musical tone signal producing means connected to said second keyboard section and including a second voltage controlled oscillator means for generating in response to the pitch determining voltage a tone signal having a frequency which is a function of the note of the operated key on said second keyboard section; sound reproducing means connected to said first and second musical tone signal producing means; and means for coupling a tone signal from said first musical tone signal producing means to said second voltage controlled oscillator means to thereby modulate the frequency of a tone signal produced by said second oscillator means.
 1. An electronic musical instrument comprising: a first keyboard section including a plurality of keys and means for generating a pitch determining voltage having a magnitude which is a function of the note of an operated key; a second keyboard section including a plurality of keys and means for generating a pitch determining voltage having a magnitude which is a function of the note of an operated key; a first musical tone signal producing means connected to said first keyboard section and including a first voltage controlled oscillator means for generating in response to the pitch determining voltage a tone signal having a frequency which is a function of the note of the operated key on said first section; a second musical tone signal producing means connected to said second keyboard section and including a second voltage controlled oscillator means for generating in response to the pitch determining voltage a tone signal having a frequency which is a function of the note of the operated key on said second keyboard section; sound reproducing means connected to said first and second musical tone signal producing means; and means for coupling a tone signal from said first musical tone signal producing means to said second voltage controlled oscillator means to thereby modulate the frequency of a tone signal produced by said second oscillator means.
 2. An electronic musical instrument according to claim 1 wherein said last-mentioned means comprises means for dividing the frequency of the tone signal from said first musical tone signal producing means.
 3. An electronic musical instrument according to claim 1 wherein said last-mentioned means comprises waveform converting means for converting the waveform of the tone signal from said first musical tone signal producing means.
 4. An electronic musical instrument according to claim 3 wherein said waveform converting means includes means to convert the waveform of the tone signal from said first musical tone signal producing means into a plurality of kinds of waveforms and includes swItching means for selecting one of the waveforms.
 5. An electronic musical instrument according to claim 1 wherein said coupling means includes means for coupling the output of said first voltage controlled oscillator means to said voltage controlled oscillator means.
 6. An electronic musical instrument according to claim 1 wherein said second musical tone signal producing means further comprises a voltage controlled filter means connected to said voltage controlled oscillator means for imparting a tone color to the tone signal from said oscillator means, said voltage controlled filter means being operative to vary in response to a control voltage the frequency characteristic thereof; and further comprising means for coupling the tone signal from said first musical tone signal producing means to said voltage controlled filter means as the control voltage.
 7. An electronic musical instrument according to claim 1 wherein said second musical tone signal producing means further comprises a voltage controlled amplifier means coupled to said second oscillator means, said amplifier means being operative to vary in response to a control voltage the gain thereof; and further comprising means for coupling the tone signal from said first musical tone signal producing means to said voltage controlled amplifier means as the control voltage.
 8. An electronic musical instrument according to claim 1 wherein said first and second keyboard sections comprise means for generating in response to key operation first and second trigger signals indicating the key operation respectively; said first musical tone signal producing means comprises a first voltage controlled filter means coupled to said first oscillator means, a first voltage controlled amplifier means coupled to said voltage controlled filter means and first control voltage generating means responsive to the first trigger signal to generate control voltages which vary as a function of time and which are coupled to said first voltage controlled oscillator means, first voltage controlled filter means and first voltage controlled amplifier means; and wherein said second musical tone signal producing means comprises a second voltage controlled filter means coupled to said second oscillator means, a second voltage controlled amplifier means coupled to said second filter means, and second control voltage generating means responsive to the second trigger signal to generate control voltages which vary as a function of time and which are coupled to said voltage controlled oscillator means, second voltage controlled filter means and second voltage controlled amplifier means.
 9. An electronic musical instrument comprising: first and second keyboard sections each having a plurality of keys; first and second musical tone signal producing means respectively coupled to said first and second keyboard sections for producing respective musical tone signals having pitch frequencies which are functions of the notes of keys operated on said respective first and second keyboard sections, at least said second musical tone signal producing means comprising a voltage controlled means for controlling at least one of the pitch frequency, tone color, and volume envelope of a musical tone signal generated by said electronic musical instrument; sound reproducing means coupled to said first and second musical tone signal producing means for generating a musical sound; and means for coupling said voltage controlled means a tone signal obtained from said first musical tone signal producing means in response to key operation on said first keyboard section for controlling said voltage controlled means.
 10. An electronic musical instrument comprising: a first keyboard section for generating a first pitch determining voltage having a magnitude which is a function of the note of an operated key and a first trigger signal indicating the key operation on said first keyboard section; a second keyboard section for generatinG a second pitch determining voltage having a magnitude which is a function of the note of an operated key and a second trigger signal indicating the key operation on said second keyboard section; a first musical tone signal producing means coupled to said first keyboard section and including a first voltage controlled oscillator means for generating in response to the pitch determining voltage from said first keyboard section a tone signal having a pitch frequency which is a function of the note of the operated key, a first voltage controlled filter means coupled to said first voltage controlled oscillator means, a first voltage controlled amplifier means coupled to said first voltage controlled filter means, and first control voltage generating means responsive to the first trigger signal to generate control voltages which vary as a function of time and which are coupled to said first voltage controlled oscillator means, voltage controlled filter means and voltage controlled amplifier means, said first voltage controlled oscillator means, voltage controlled filter means and voltage controlled amplifier means being operative to vary in response to the control voltages, the oscillator frequency of said first voltage controlled oscillator means, the frequency characteristic of said first voltage controlled filter means and the gain of said first voltage controlled amplifier means; a second musical tone signal producing means coupled to said second keyboard section and including a second voltage controlled oscillator means for generating in response to the pitch determining voltage from said second keyboard section a tone signal having a pitch frequency which is a function of the note of the operated key, a second voltage controlled filter means coupled to said second voltage controlled oscillator means, a second voltage controlled amplifier means coupled to said second voltage controlled filter means, and a second control voltage generating means responsive to the second trigger signal to generate control voltages which vary as a function of time and which are coupled to said second voltage controlled oscillator means, voltage controlled filter means and voltage controlled amplifier means, said second voltage controlled oscillator means voltage controlled filter means and voltage controlled amplifier means being operative to vary in response to the control voltages the oscillation frequency of said second voltage controlled oscillator means, the frequency characteristic of said second voltage controlled filter means and the gain of said second voltage controlled amplifier means; second reproducing means coupled to said first and second musical tone signal producing means; and means for coupling as an additional control voltage an output signal from said first voltage controlled oscillator means in said first musical tone signal producing means to at least one of said second voltage controlled oscillator means, second voltage controlled filter means and second voltage controlled amplifier means in said second musical tone signal producing means.
 11. An electronic musical instrument according to claim 10 wherein said last-mentioned means comprises switching means for selectively coupling the output signal from said first voltage controlled oscillator means to one of said second voltage controlled oscillator means, second voltage controlled filter means and second voltage controlled amplifier means.
 12. An electronic musical instrument according to claim 10 wherein said last-mentioned means comprises means for dividing the frequency of the output signal from said first voltage controlled osicllator means, means. 